The subject of the present invention is a combined hob consisting of a body and numerous machining elements situated in the seats within the said body.
Known combined hobs are manufactured in a form of a cylindrical body containing the seats of rectangular sections, designed for fixing the machining segments. In order to make a microsection of the flank faces of the machining segments, strips of rectangular sections are fixed in the seats, with the aforesaid machining segments supported on the strips. The segments so located are offset from the center of the body, and the outer diameter of the tops of their profiles is bigger. The segments so assembled are subjected to grinding in order to shape their flank faces. Then the distance strips are removed and each of the aforesaid segments is fixed stably in the same seat, in place of the removed strips.
The segments so mounted form a hob whose diameter is smaller than it is during the machining of the flank faces of the said segments.
As a result of this operation, the required relief angle of each machining segment is obtained.
The seats of rectangular section in the body of the hob, containing at least two accurately parallel planes, require the machining segments with catching elements formed by the two parallel planes, accurately fitted to the seat with respect to parallelism and the distance between the planes. Maintenance of these parameters is expensive and especially increases the production costs. If these high requirements are not met, there is a decrease in the accuracy of hob mounting, which reduces its usefulness and strength. Both the seats and the catching elements of the machining segments have three planes mutually dependent on one another and requiring separate grinding.